German Patent No. 32 10 770 discloses for the production of substantially spherical lightweight particles of metal, a process in which particles of foamed plastics, such as commercially available expanded polystyrene, are metallized, e.g., with copper, silver or nickel in an electroless process and the plastic cores are pyrolytically decomposed at temperatures of about 400.degree. C. The wall thickness of the particles can be electrochemically increased to about 0.05 mm by electrodeposition thereon.
Published German Application No. 23 55 498 discloses for the production of a catalyst carrier consisting of a spongelike ceramic body a process in which foamed polystyrene spheres packed in a bed are bonded at their contacting surfaces at elevated temperatures to form a skeleton of spheres, and the interstices of the skeleton of spheres are completely filled with an aqueous suspension of ceramic material, the ceramic material filling the interstices of the skeleton of spheres is dried, the foamed polystyrene spheres are removed by pyrolysis and the remaining ceramic skeleton is heated nd sintered at temperatures from 1000.degree. to 1500.degree. C. The ceramic material which is used can consist of highly reactive alumina or of alumina and e.g. of highly reactive alumina or of alumina and bentonite. A dispersing agent is added to the ceramic dispersion in order to increase its fluidity.
European Patent Publication No. 119,913 discloses for the production of inorganic porous bodies a process in which spheres are produced of a porous material and have been coated with an organic binder, such as a thermoplastic polymer and with an inorganic material, such as metal or ceramics. The coated spheres are compacted cold to form a shaped body, which is heat-treated in a vacuum in order to vaporize the porous material and the organic binder, and the resulting hollow spheres are subsequently sintered.
French Patent No. 1,266,824 discloses for the production of porous metal bodies a process in which an organic binder, such as methyl methacrylate, is added to a mixture or a fine metal powder and organic particles consisting of hollow microspheres made of phenol-formaldehyde resin or other organic substances, the hardened mixture is heat-treated to vaporize the organic hollow microspheres and the organic binder and the resulting hollow spheres of metal are subsequently sintered.